Dihydrogen Adduct (Co–H₂) Complexes Displaying H‐Atom and Hydride Transfer

Abstract

Abstract The prototypical reactivity profiles of transition metal dihydrogen complexes (M‐H 2 ) are well‐characterized with respect to oxidative addition (to afford dihydrides, M(H) 2 ) and as acids, heterolytically delivering H + to a base and H − to the metal. In the course of this study we explored plausible alternative pathways for H 2 activation, namely direct activation through H‐atom or hydride transfer from the σ‐H 2 adducts. To this end, we describe herein the reactivity of an isostructural pair of a neutral S = and an anionic S =0 Co‐H 2 adduct, both supported by a trisphosphine borane ligand (P 3 B ). The thermally stable metalloradical, (P 3 B )Co(H 2 ), serves as a competent precursor for hydrogen atom transfer to t Bu 3 ArO ⋅ . What is more, its anionic derivative, the dihydrogen complex [(P 3 B )Co(H 2 )] 1− , is a competent precursor for hydride transfer to BEt 3 , establishing its remarkable hydricity. The latter finding is essentially without precedent among the vast number of M‐H 2 complexes known.